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  • 1
    Electronic Resource
    Electronic Resource
    Magnetic properties of Fe/Pd multilayers grown by electron-beam evaporation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 3965-3970 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of [Fe(20 A(ring))/Pd(x A(ring))]25 multilayers prepared by ultrahigh vacuum electron-beam evaporation are presented. It is found that the crystal structure of Fe layers change from bcc to fcc when the thickness of Pd layers dPd≥36 A(ring). The saturation magnetization per unit Fe volume at 5 K is enhanced and oscillates with the increment of the thickness of Pd layers, due to the polarization of Pd atoms. The magnetic hysteresis loops of samples indicate low coercive forces, and ferromagnetic coupling between the Fe layers for all Pd thicknesses (6–60 A(ring)). The conversion electron Mössbauer spectra measurements proved that the magnetic moment of fcc Fe is the same as that of the bcc Fe. It is also found that the magnetic anisotropy dependence on dPd is similar to that of the saturation magnetization, and relates to the Fe layer structure transition. The Curie temperature of Fe/Pd multilayers decreases monotonously with the increasing of dPd. The low temperature magnetization measurement of Fe/Pd multilayers suggests that the interlayer coupling between Fe layers and polarization of Pd layers influences the temperature dependence of saturation magnetization. No evidence of antiferromagnetic coupling between Fe layers and giant magnetoresistance effect is found. The relationship among structure, polarization of Pd layers, and magnetic coupling is discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358579
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  • 2
    Electronic Resource
    Electronic Resource
    Carrier transport in porous silicon light-emitting devices (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 295-300 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This work presents a comprehensive investigation of carrier transport properties in light-emitting porous silicon (LEPSi) devices. Models that explain the electrical characteristics and the electroluminescence properties of the LEPSi devices are developed. In metal/LEPSi devices, the forward current density–voltage (J–V) behavior follows a power law relationship (J∼Vm), which indicates a space charge current attributed to the carriers drifting through the high resistivity LEPSi layer. In LEPSi pn junction devices, the forward J–V behavior follows an exponential relationship (J∼eeV/nkT), which indicates that the diffusion of carriers makes a major contribution to the total current. The temperature dependence of the J–V characteristics, the frequency dependence of the capacitance–voltage characteristics, and the frequency dependence of the electroluminescence intensity support the models. Analysis of devices fabricated with a LEPSi layer of 80% porosity results in a relative permittivity of ∼3.3, a carrier mobility of ∼10−4 cm2/V s, and a free carrier concentration of ∼1013 cm−3. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362783
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  • 3
    Electronic Resource
    Electronic Resource
    Quasi-donor-acceptor pair photoluminescence emission in GaxIn1−xAs/InP (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2427-2430 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low-temperature properties of the excitation-dependent photoluminescence emission, in nominally undoped n-type GaxIn1−x As (0.44≤x≤0.48) layers grown on InP by molecular-beam epitaxy, are investigated with changes of temperature and excitation intensity. The excitation-dependent emission is attributed to the quasi-donor-acceptor pair transition in impure compensated crystals. The random impurity potential arising from residual impurities causes a larger energy shift than expected for the usual donor-acceptor pair transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342811
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  • 4
    Electronic Resource
    Electronic Resource
    Extremely low nonalloyed and alloyed contact resistance using an InAs cap layer on InGaAs by molecular-beam epitaxy (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 429-431 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Extremely low alloyed and nonalloyed ohmic contact resistances have been formed on n-type InAs/In0.53Ga0.47As/In0.52Al0.48As structures grown on InP(Fe) by molecular-beam epitaxy. To insure the accuracy of the small contact resistances measured, an extended transmission line model was used to extrapolate contact resistances from test patterns with multiple gap spacings varying from 1 to 20 μm. For a 150-A(ring)-thick InAs layer doped to 2×1018 cm−3 and a 0.1-μm-thick InGaAs layer doped to 1×1018 cm−3, a specific contact resistance of 2.6×10−8 Ω* cm2 was measured for the nonalloyed contact, while a resistance less than 1.7×10−8 Ω* cm2 is reported for the alloyed contact. Conventional Au-Ge/Ni/Au was used for the ohmic metal contact and alloying was performed at 500 °C for 50 s in flowing H2. Using a thermionic field emission model, the barrier height at the InAs/InGaAs interface was calculated to be 20 meV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341210
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  • 5
    Electronic Resource
    Electronic Resource
    Optical reflectance in GaAs/AlGaAs quantum wells (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 3847-3850 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Molecular-beam epitaxial GaAs/AlGaAs bulk layers and quantum well heterostructures have been grown and characterized at 3 K using broadband optical reflectance and photoluminescence spectroscopy. Reflectance spectra display sharp, well-defined features due to strong near-band gap excitonic effects that cause the reflectance to deviate by over 50% from the bulk value in some cases. Features due to impurity-bound excitons, free-to-bound transitions, and free excitons have all been identified in quantum well heterostructures. Interband transitions involving the n=1 light hole and higher-lying subbands are much more readily observed in reflectance spectra than in photoluminescence, including "forbidden'' Δn≠0 transitions. Additionally, reflectance has been used to probe the interfaces, revealing fine structure due to monolayer and submonolayer deviations in well thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336726
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  • 6
    Electronic Resource
    Electronic Resource
    Characterization of graded interface InxGa1−xAs/In0.52Al0.48As (0.53〈x〈0.70) structures grown by molecular-beam epitaxy (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 62 (1987), S. 2880-2884 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Modulation doped InxGa1−xAs/In0.52Al0.48As/InP structures were grown by molecular-beam epitaxy with x values between 53% and 70%. For pseudomorphic cases, graded instead of abrupt interfaces were used. Hall mobility and persistent photoconductivity measurements as a function of temperature were used to characterize samples with different structural parameters. Consistent trends in the variation of mobilities and two-dimensional carrier concentration (n2D ) under light and dark conditions have been observed and discussed in terms of applicable scattering mechanisms. The Hall mobilities are comparable to the best results obtained to date but with significantly higher n2D concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.339397
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  • 7
    Electronic Resource
    Electronic Resource
    Evolution of mosaic structure in Si0.7Ge0.3 epilayers grown on Si(001) substrates (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1292-1297 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article, we report a study of mosaic structures in partially relaxed Si0.7Ge0.3 epilayers grown on Si(001) substrates by x-ray double- and triple-axis diffractometry. The samples have different layer thicknesses and hence different degrees of strain relaxation. Our results show that, at early stages of strain relaxation, the films contain mosaic regions laterally separated by perfect regions. This is because the mosaic structure caused by a misfit dislocation is effectively localized in a lateral range of the layer thickness. Therefore, far from the dislocations, the film is virtually a perfect crystal. With the increase in the degree of strain relaxation, and consequently in the dislocation density, the mosaic regions of the layer expand while the perfect regions shrink and finally vanish completely. Moreover, our results indicate that the conventional method of estimating dislocation density from the x-ray rocking curve width fails in our case. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370884
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  • 8
    Electronic Resource
    Electronic Resource
    The frequency response of porous silicon electroluminescent devices (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2515-2517 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Under a constant forward bias, porous silicon light-emitting devices (LEDs) produce stable electroluminescence (EL) that is detectable at applied voltages as low as 5 V and visible in daylight at higher voltages. The recombination dynamics of the EL are studied and correlated to the photoluminescence properties of light-emitting porous silicon (LEPSi). The EL efficiency is related to the LEPSi properties and the device configuration. LEPSi LEDs with an EL efficiency of 0.01% have been achieved. The frequency response of the EL to a modulating ac bias is measured. For metal/LEPSi LEDs, the −3 dB frequency is determined by the carrier transit time which must be larger than the carrier lifetime to achieve efficient EL. For LEPSi pn junction LEDs, the −3 dB frequency is determined only by the carrier lifetime and can be in excess of 200 kHz. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114443
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  • 9
    Electronic Resource
    Electronic Resource
    T8-Hydridospherosiloxanes: novel precursors for silicon dioxide thin films. 1. Precursor characterization and preliminary CVD (1993)
    s.l. : American Chemical Society
    Chemistry of materials 5 (1993), S. 1636-1640 
    Details
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/cm00035a009
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  • 10
    Electronic Resource
    Electronic Resource
    Quantification of scaling exponents and crossover phenomena in nonstationary heartbeat time series (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 5 (1995), S. 82-87 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The healthy heartbeat is traditionally thought to be regulated according to the classical principle of homeostasis whereby physiologic systems operate to reduce variability and achieve an equilibrium-like state [Physiol. Rev. 9, 399–431 (1929)]. However, recent studies [Phys. Rev. Lett. 70, 1343–1346 (1993); Fractals in Biology and Medicine (Birkhauser-Verlag, Basel, 1994), pp. 55–65] reveal that under normal conditions, beat-to-beat fluctuations in heart rate display the kind of long-range correlations typically exhibited by dynamical systems far from equilibrium [Phys. Rev. Lett. 59, 381–384 (1987)]. In contrast, heart rate time series from patients with severe congestive heart failure show a breakdown of this long-range correlation behavior. We describe a new method—detrended fluctuation analysis (DFA)—for quantifying this correlation property in non-stationary physiological time series. Application of this technique shows evidence for a crossover phenomenon associated with a change in short and long-range scaling exponents. This method may be of use in distinguishing healthy from pathologic data sets based on differences in these scaling properties. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166141
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